Methods and articles for preventing clotting of blood

ABSTRACT

A method for preventing the formation of clots in blood in contact with synthetic articles and preventing deterioration of said synthetic articles involving coating the entire blood contacting surface of said articles with a layer of molybdenum and placing the molybdenum coated surface of said article in contact with blood. The present invention is well adapted to be utilized in replacing cardio-vascular organs such as blood vessels and heart valves because the molybdenum coated articles of this invention are flexible, will last indefinitely when in contact with blood, will not react with the blood and are nonthrombogenic.

Unite Alfano States Patent [4 1 Sept. 5, 1972 [54] METHODS AND ARTICLES FOR PREVENTING CLOTTING OF BLOOD [21] Appl. No.: 73,193

[52] US. Cl ..3/1, 3/DIG. l, 3/DIG. 3, 128/334 R, 128/272, 117/107.2 R, 117/160 [51] Int. Cl ..A61f l/24, A61f1/22 [58] Field of Search ..3/1, DIG. l, DIG. 3;

128/334 R, 335.5, 214, 214.4, 272; 117/95, 107, 107.2 R, 160, 138.8 N

[56] References Cited OTHER PUBLICATIONS A New Plastic Interface which has Antithrombotic Characteristics and Appears to Mimic the Vascular Interface by P. N. Sawyer et al., Trans. Amer. Soc. Artif. Int. Organs, Vol. XII, 1966, pages 183- 186.

Aluminum Prostheses as Blood Vessel Replacements by W. J. McCann et al., Surgery, Vol. 61, No. 4 pp. 588- 590, April 1967.

Oxidation Potentials of Elements, Handbook of Chemistry and Physics, (Chemical Rubber Publishing Co.), 43rd, ed., 1961, page 1740.

Primary ExaminerRichard A. Gaudet Assistant Examiner-Ronald L. Frinks Att0rney-Miketta, Glenny, Poms and Smith [57] ABSTRACT A method for preventing the formation of clots in blood in contact with synthetic articles and preventing deterioration of said synthetic articles involving coating the entire blood contacting surface of said articles with a layer of molybdenum and placing the molybdenum coated surface of said article in contact with blood. The present invention is well adapted to be utilized in replacing cardio-vascular organs such as blood vessels and heart valves because the molybdenum coated articles of this invention are flexible, will last indefinitely when in contact with blood, will not react with the blood and are nonthrombogenic.

8 Claims, No Drawings METHODS AND ARTICLES FOR PREVENTING CLOT'IING OF BLOOD BACKGROUND OF THE INVENTION ment requires the use of external instruments to main- 1 tain life during the surgical repair.

At present, the normal method for replacing defective portions of blood vessels is to utilize a plastic (e.g. nylon) tube which is preferably connected to the remaining blood vessel by stitches via a sleeve made of Velour. Unfortunately, it is necessary to replace the plastic tubing about every three years because the blood reacts with the plasticizers in the plastic thereby causing deterioration of the tube. Moreover, and probably more importantly, the blood has a tendency to clot when in contact with synthetic, i.e. non-biological materials e. g. nylon. This of course can be very dangerous in that a clot can cause death by blocking either the implanted synthetic blood vessel or breaking loose to block coronary or brain blood supplies. Also, if the nylon does deteriorate, the surface which was originally smooth has a tendency to become pitted. This causes eddies in the blood which is very undesirable. The release of plasticizers into the blood stream cause cell damage leading to anemia in acute cases.

Similarly, the methods and materials now utilized to replace heart valves (both ball and discoid valves) have not been entirely satisfactory. For example, heart valves need to be flexible, non-corrosive, non-thrombogenic, and inert generally to body fluids. As a general rule, the material now being utilized to provide such valves is Silastic which is a composition containing organosilicon polymers. Valves made from Silastic are deformable but nevertheless are unsatisfactory because they are thrombogenic and rapidly deteriorate when in contact with blood and other body fluids so that it is necessary to replace the valves at least every 3 years. This, of course, is a serious disadvantage.

In addition to the attempts to develop a satisfactory method for replacing blood vessels and heart valves, prior art workers have attempted to develop a material which can be utilized to store blood, to remove blood, and to circulate blood into and from the body for various purposes. A satisfactory material for this purpose must be inexpensive, flexible (when utilized as a tube for transferring blood either to or from the body), not be adversely affected by the blood and, most importantly, be non-thrombogenic for long periods of time as well as not damaging blood cells.

It is thus a desideratum in the art to provide methods and articles for storing blood for long periods, for circulating blood for long periods, replacing blood vessels and heart valves in a simple manner, and, at the same time, eliminating the need for replacing synthetic blood vessels and heart valves for indefinite periods of time.

SUMMARY OF THE INVENTION The primary object of the present invention therefore is to disclose and provide a method for easily and efficiently replacing blood vessels and heart valves, as well as handling blood, in such a manner that the blood will not form clots, will not be affected by the replacement articles, and which will last indefinitely.

It is a further object of the present invention to disclose and embody the coating of preformed synthetic articles for replacing blood vessels of the body, which are non-thrombogenic, are not corroded or otherwise affected by the blood or other body fluids, are ductile,

and which will last indefinitely so that there is no need 0 to replace same.

It is still another object of the present invention to disclose a method for replacing heart valves so that said heart valves will not have to be replaced again for an in: definite period of time and will not adversely affect the blood, such as the formation of blood clots.

It is still another and further object of the present invention to provide a method for easily storing and handling blood for long periods of time with no formation of blood clots.

Still another object of the present invention is to provide preformed synthetic articles coated with a thin, very smooth surface of molybdenum, the molybdenum coating being securely adhered to the substrate, said preformed articles being utilized for storing blood, transferring blood, and replacing members of the cardio-vascular system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing objects, and others, are accomplished by the present invention which, generally stated, comprises coating preformed synthetic articles of a designated weight and shape with a thin layer of molybdenum on those surfaces of the articles which will be in contact with blood or other body fluids.

The term synthetic article or material, when used in the specification and claims, refers to an article or material which is non-biological, i.e. not formed by a biological entity without modification.

When utilizing the articles of the present invention to replace blood vessels it is necessary that they have the following qualities and characteristics:

1. flexibility;

2. smoothness in order to reduce friction;

3. relatively high strength;

4. inert to the blood;

5. long lasting; and, most importantly,

6. non-thrombogenic.

I have discovered that when a thin coating of molybdenum is placed on a plastic tube the thus produced article has the above characteristics.

Surprisingly, of all the metals tested only molybdenum possesses all of the characteristics necessary to produce an article which can come in contact with blood without affecting the blood and without causing the blood to form clots. In addition, molybdenum can be coated on almost any composition and the resulting article maintains its original flexibility. In addition, molybdenum coated on any article will not scale off even when in contact with blood for long periods of time. For example, blood contained in a glass test tube which had been coated with molybdenum did not form any clots, nor could there be found any molybdenum in the blood even after 288 hours. Just as importantly, for use in replacing defective blood vessels, is the fact that the surface of the molybdenum coating was not corroded or pitted in any way because of its exposure to blood.

In a preferred exemplary embodiment molybdenum was coated on a nylon tube, the size of the tube being suitable to replace defective blood vessels in the body. The molybdenum can be coated on both sides of the nylon tube in any convenient manner well known in the art and the present invention is not predicated per se on the method of coating molybdenum on a substrate. However, in the interest of clarity, one of the preferred methods of coating molybdenum on plastics such as nylon or Silastic, is vacuum deposition utilizing molybdenum carbonyl as the molybdenum source and, as an energy source, high intensity light from a meser or laser.

Other methods may be utilized to coat the plastic substrate such as heating the molybdenum carbonyl to its vaporization point via a filament instead of a laser beam and allowing the vapors of molybdenum to contact the substrate while it is being moved thereby forming a thin film of molybdenum on said substrate.

It is found that a thin film of molybdenum completely covers the plastic substrate, the filmbeing anywhere from two atoms thick to 5 angstroms up to 0.003 inches. I have discovered that the thin film of molybdenum is securely adhered to the plastic substrate and cannot be easily removed. Moreover, both the nylon and Silastic retain their original properties in that the final article is flexible and deformable and, in addition, the final article has as much strength as the original substrate.

A nylon tube coated both on the inside and the outside with a thin film of molybdenum is utilized to replace defective blood vessels preferably utilizing a laser beam in the same manner as retinas are now attached. If desired, the vessel ends could be attached to a sleeve made of Velour. A sleeve made of Velour is non-thrombogenic but does not have the strength necessary to be utilized in replacing blood vessels. Therefore utilizing the molybdenum coated. tube for replacing blood vessels, either per se or via a sleeve made of Velour, would possess the requisite flexibility and strength but be impervious to corrosion or other deterioration by attack from the blood or other body fluids and would be non-thrombogenic. Based on present tests blood vessels replaced in such a manner would appear to be able to last indefinitely without needing replacement; and at least three times as long as synthetic blood vessels made of nylon or the like.

As noted supra, the present invention also contemplates replacing other organs of the cardio-vascular system such as heart valves. For example, heart valves are now made from a material such as Silastic which possesses the necessary deformability and strength. However, Silastic readily deteriorates upon being contacted by blood and, in addition, is not completely nonthrombogenic. Therefore, there is some danger when utilizing heart valves (either discoid or ball) made of Silastic because of the possibility of the formation of blood clots but, most importantly, is the fact that they possess a high stren th, are deformable, and are im er- VlOUS to attack by b ood. Such valves have an lnde nite life when inserted into the heart without any possibility of forming blood clots.

The articles of this invention can also be utilized to store blood as for example by coating a glass container with molybdenum. If blood is merely placed in a glass container with no coating blood clotting is seen in 12 minutes at 25 C. and 37 C. However, no clots were formed in blood placed in a molybdenum coated glass container.

The present invention has been described with reference to certain preferred exemplary embodiments; however, it is emphasized that the invention is not to be limited thereto since many other embodiments will be apparent to the art skilled.

I claim:

1. A method for preventing deterioration of synthetic articles in contact with blood and preventing the formation of blood clots in said blood comprising coating the entire surface of a substrate, which is to be in contact with blood, with a thin layer of molybdenum in an amount sufficient to prevent clotting of the blood and deterioration of the article and placing the synthetic article in contact with blood.

2. A method according to claim 1 wherein the substrate is plastic.

3. A method according to claim 1 wherein the substrate is nylon.

4. A method according to claim 2 wherein the plastic is nylon 5. A method for replacing a defective blood vessel in an animal body which comprises removing the defective blood vessel from the remaining portion of the non-defective blood vessel and replacing the defective blood vessel with a flexible plastic tube of a length and diameter of the defective blood vessel, the surface of said plastic tube which is to be in contact with blood having a thin layer of molybdenum thereon by connecting same to the remaining portion of the blood vessel.

6. A non-thrombogenic synthetic blood vessel for use in animals to replace a portion of a blood vessel which is defective comprising:

a flexible tube having an internal diameter generally the same as the diameter of the blood vessel to be replaced and having a corresponding length;

said flexible tube having a thin coating of molybdenum continuously on the inner and outer surfaces of said tube whereby said tube is protected from attack by blood and the blood flowing therethrough is prevented from forming clots.

7. A synthetic blood vessel according to claim 6 wherein said flexible tube is plastic.

8. A synthetic blood vessel according to claim 7 wherein said plastic is nylon. 

2. A method according to claim 1 wherein the substrate is plastic.
 3. A method according to claim 1 wherein the substrate is nylon.
 4. A method according to claim 2 wherein the plastic is nylon
 5. A method for replacing a defective blood vessel in an animal body which comprises removing the defective blood vessel from the remaining portion of the non-defective blood vessel and replacing the defective blood vessel with a flexible plastic tube of a length and diameter of the defective blood vessel, the surface of said plastic tube which is to be in contact with blood having a thin layer of molybdenum thereon by connecting same to the remaining portion of the blood vessel.
 6. A non-thrombogenic synthetic blood vessel for use in animals to replace a portion of a blood vessel which is defective comprising: a flexible tube having an internal diameter generally the same as the diameter of the blood vessel to be replaced and having a corresponding length; said flexible tube having a thin coating of molybdenum continuously on the inner and outer surfaces of said tube whereby said tube is protected from attack by blood and the blood flowing therethrough is prevented from forming clots.
 7. A synthetic blood vessel according to claim 6 wherein said flexible tube is plastic.
 8. A synthetic blood vessel according to claim 7 wherein said plastic is nylon. 